A magnetic card reader which performs reading and writing magnetic data from and on a magnetic card is commonly mounted in an ATM or the like, which is, for example, installed in a bank. The magnetic card reader includes a card slot for inserting and ejecting a magnetic card, a detector for detecting the magnetic card which has been inserted from the card slot, a card introducing passage on which the magnetic card inserted from the card slot is guided to the inside of the magnetic card reader, and a shutter for opening or closing the card introducing passage.
First, a user inserts a tip end of a magnetic card into the card slot. Then, the insertion of the magnetic card is detected by the detector, and the shutter having closed the card introducing passage is opened and, at the same time, the magnetic card is taken into the inside of the magnetic card reader by rollers provided in the card introducing passage. In the magnetic card reader, the taking-in operation of a magnetic card is performed in this manner.
Recently, a device which illegally reads information recorded on a magnetic card has been becoming a social problem. The illegal reading device is disposed at the front (outside) of the card slot of the magnetic card reader and provided with a magnetic head for illegally reading information recorded on the magnetic card. When a magnetic card is inserted into the card slot (a pseudo-card slot) of the magnetic card reader on which an illegal reading device is mounted, information recorded on the magnetic card is read by the magnetic head without being perceived by a user.
Therefore, medium processing devices have been developed which are provided with a function for preventing illegal reading from a magnetic card. As an example of such the medium processing devices, a magnetic card transaction device has been disclosed, for example, in Japanese Patent Laid-Open No. 2001-67525. The magnetic card transaction device disclosed in this reference is provided with a reflecting type photo sensor which detects a foreign matter (illegal reading device) fitted to the vicinity of the card slot. The reflecting type photo sensor is disposed on the inner side of a front panel which partitions the outside from the inside of the device. A light-transmitting hole for detecting a foreign matter is formed on a front side of the reflecting type photo sensor in the front panel.
When the magnetic card transaction device structured as described above is used, in the event that a foreign matter is fitted to the vicinity of the card slot, the light quantity of a light beam, which is emitted from a light emitting body and is incident on the reflecting type photo sensor through the light-transmitting hole, is varied and thus the fitting of the foreign matter can be detected. Therefore, in this case, an alarm signal is transmitted to a host device, or a shutter that opens or closes a card introducing passage has been kept closed, and thus illegal reading from a magnetic card can be prevented.
However, in the magnetic card transaction device disclosed in the above-mentioned reference, when an illegal person who is going to attach a foreign matter notices the light-transmitting hole, it is conceivable that the person takes an action to suspend the illegal reading preventing function, for example, by damaging the reflecting type photo sensor disposed in the inside of the light-transmitting hole or causing unnecessary light beam to be incident into the light-transmitting hole. Therefore, in order to maintain the illegal reading preventing function and improve the reliability of a magnetic card reader, it is necessary to develop a technique with which the presence of the reflecting type photo sensor is difficult to be recognized from the outside.
Further, in the conventional technique with which the variation of the light quantity is detected with the reflecting type photo sensor through the light-transmitting hole as described above, an erroneous detection due to external (outside) light such as sunlight or indoor fluorescent lamps may occur depending on the environment where the magnetic card reader is installed.